Cross Influence of Coordinate and Slope Related Fringes during Shearographic Profiling

Abstract

In this paper, an optical technique based on speckle-shearing interferometry is employed for the measurement of surface coordinates and slopes. By the double exposure technique and shifting the light source in a prescribed manner between the exposures, carrier and slope related fringes are generated. The surface coordinates and slopes are determined from the carrier and slope fringes respectively. Theoretical derivation shows that the resulting fringe pattern is a mixture of both carrier and slope fringes. The mutual influence of each parameter (carrier and slope) on the resulting fringe pattern is studied. The results demonstrate that the slope parameter has a dominating influence on the resulting fringe pattern. Experimental results conducted on objects of known shapes compare favourably with the computed fringe patterns. Copyright © 1996 Elsevier Science Ltd.